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Summary of Build A Smart LED Flashlight Using Arduino
The article describes a light-sensing LED flashlight that automatically turns on for 60 seconds in darkness and can be manually extended 60 seconds via an RST button. It includes schematics, PCB assembly, BOM under $5, tools, and step-by-step SMD soldering instructions; specs cover 3 white LEDs, a 16-bit ultra-low-power TI microcontroller, 3V 140mAh battery, low standby current, and compact PCB dimensions.
Parts used in the Light Sensing LED Flashlight:
- LED1 - White LED
- LED2 - White LED
- LED3 - White LED
- R1 - Current limit resistor for LED1
- R2 - Current limit resistor for LED2
- R3 - Current limit resistor for LED3
- U1 - 16-bit ultra low power microcontroller (Texas Instruments)
- R4 - Power-on resistor
- C1 - Power-on capacitor
- S1 - Manual Reset push-button (RST)
- PH1 - Light sensor (photo sensor)
- R5 - Resistor for light sensor voltage divider
- 3V battery, 140mAh
- PCB - FR-4 board, 20mm x 26.25mm
How it works:
The flashlight turns on automatic for 60 seconds when it senses that the room is dark enough.
To turn on manual light for additional 60 seconds you need to push the RST button.
The Light sensing LED Flashlight is invaluable for emergencies such as power failures or blackouts.
Step 1: The Flashlight Is Invaluable for Emergencies Such As Power Failures or Blackouts.
I have assembly several Flashlight, and have several dozen spear PCB board and components that I can share with any one who wish to make the flashlight.
The instructable contains:
- Flashlight schematic,
- PCB Assembly drawing,
- BOM – Components KIT cost less than $5
- Tools list
- Detailed step-by- step assembling instructions.
Specifications:
- Number of flashlight components: 15
- Color of LED’s light: white
- Number of LEDs: 3
- Light Distance: 2-3 meters
- Size of flashlight : 26.25mm x 20mm x 5mm
- Current consumption :
- LEDs turn ON: 4-5mA
- LEDs turn OFF: 30-45uA
- Battery capacity: 140mAh
- Battery voltage: 3V
- Battery life : up to 6 months (if flashlight turns on 2 times for 60 sec in 24 hours)
- Required skills : knowledge of soldering SMD components
Step 2: Light Sensing LED Flashlight Schematics
The Light sensing LED Flashlight Schematics contains the next blocks:
- 3 White LEDs (LED1 – LED3) and 3 current limit resistors (R1 – R3)
- 16 bit ultra low power micro-controller of firm Texas Instruments (U1)
- Power on (R4 and C1) and manual Reset (S1 push-button) micro-controller circuit
- Light sensor (PH1) and resistor R5 – is voltage divider circuit
- Flashlight battery 3V, 140mAh
Step 3: The Light Sensing LED Flashlight PCB
I ordered the PCB from a Chinese low cost prototype PCB manufacturer.
The PCB Specification are:
- Dimensions: 20mm x 26,25mm
- Layers number :2 Layers
- PCB Type: Normal FR-4 Board
- FR4-TG: TG 130-140
- Thickness: 1.6mm
- Solder Mask: White
- Silkscreen: Black
- Surface Finish: HASL with lead
- Finished Copper: 1 oz Cu
Read more: Build A Smart LED Flashlight Using Arduino
- How long does the flashlight turn on automatically when it senses darkness?
The flashlight turns on automatically for 60 seconds when it senses the room is dark enough. - Can I extend the light manually and how?
Yes. Press the RST push-button to turn on manual light for an additional 60 seconds. - How many LEDs are used and what color are they?
The project uses three white LEDs. - What microcontroller is used in the flashlight?
A 16-bit ultra low power microcontroller from Texas Instruments (U1) is used. - What is the battery specification and expected battery life?
The battery is 3V with 140mAh capacity and can last up to 6 months if the flashlight turns on twice for 60 seconds each day. - What is the current consumption when LEDs are on and off?
When LEDs are on the current is 4-5 mA; when off the current is 30-45 µA. - What are the PCB dimensions and type?
The PCB dimensions are 20 mm x 26.25 mm, 2-layer FR-4 board with 1.6 mm thickness. - How many components are there in the flashlight?
The flashlight uses 15 components. - What soldering skills are required to assemble the flashlight?
Knowledge of soldering SMD components is required. - What documentation is included in the instructable?
The instructable includes the flashlight schematic, PCB assembly drawing, BOM with kit cost under $5, tools list, and detailed step-by-step assembly instructions.
